Electrical connector having improved contact elements

ABSTRACT

An electrical connector includes an insulative base ( 8 ) defining a plurality of contact receiving bores ( 81 ) for each receiving a contact element ( 9 ) therein. A cover plate ( 5 ) is attached to the base to define a space therebetween for movably receiving a slide plate ( 7 ). The slide plate defines a plurality of slots ( 72 ) corresponding to the contact receiving bores of the base and each slot retains a conductive member ( 70 ) therein. The cover plate defines holes ( 51 ) therein corresponding to the slots and adapted to guide pins ( 4 ) of a chip module into the slots. The slide plate is moveable between a released position and an engaged position where the conductive member engages with both the pin and the contact element to establish electrical connection therebetween. Each contact element includes a soldering section ( 92 ) extending beyond the base and adapted to be soldered to a circuit board ( 3 ), and an engaging section ( 93 ) extending into the corresponding slot for being engaged by the conductive member. A retention section ( 91 ) fixed in the base is spaced from and connected to the soldering section by a connection section ( 910 ) thereby allowing a reduction of thickness of the connector without sacrificing the mechanical strength thereof. The connection section is resiliently deformable to accommodate a relative movement between the retention section and the soldering section caused by a difference in thermal expansion between the connector and the circuit board.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an electrical connector, andin particular to a zero insertion force (ZIF) ball grid array (BGA)connector having firmly secured contact elements for effectively formingan electrical connection with pins of a chip module.

2. The Prior Art

Chip modules have been improved significantly. The amount and speed ofdata transferred by the chip modules has increased rapidly. Thus, acorresponding modification of a connector connecting the chip module toa circuit board is required. Corresponding examples are disclosed inTaiwan Patent Application Nos. 83207257, 83208396, 83212080 and83212081.

FIGS. 1A, 1B, 1C and 1D show a conventional connector wherein FIGS. 1Aand 1C are top views of a portion of the connector while FIGS. 1B and 1Dare corresponding cross-sectional views. The conventional connectordefines a number of contact receiving holes 21 in an insulative body 2for retaining contact elements 1 therein. Each contact element 1 has anelongate body 10 comprising an engaging section 11 at one end and aretention section 12 at an opposite end. A soldering section 13 furtherextends from the retention section 12 and protrudes beyond the body 2for being soldered to a circuit board 3 by solder 31. The retentionsection 12 comprises barbs 121 for engaging with an inside surface ofthe contact receiving hole 21 to secure the contact element 1 therein.

Pins 4 of a chip module are inserted into the contact receiving holes 21of the body 2 but are initially separated from the contact elements 1.The chip module is then moved relative to the body 2 to bring the pins 4into contact with contact elements 1 as shown in FIGS. 1C and 1D wherebythe pins 4 are electrically connected to the contact elements 1.

A disadvantage associated with the conventional connector is that duringthe movement of the chip module, a great force is applied to the contactelement 1 by the pin 4 which in turn induces a large moment at theretention section 12. The retention section 12 may thus be moved andseparated from the body 2 as shown in FIG. 1D, causing damage to thesolder 31 connection.

Furthermore, since the retention section 12 and the soldering section 13are immediately adjacent to each other, a strain may be induced on thesolder 31 connection due to a difference in thermal expansion of theinsulative body 2 and the circuit board 3. The strain may sometimescause breakage of the solder 31 connection. In addition, the retentionsection 12 and the soldering section 13 are vertically stacked on eachother thereby hindering a reduction of the thickness of the insulativebody 2 while maintaining the same mechanical strength when securing theretention section 12 in the contact receiving hole 21.

It is thus desirable to have an electrical connector that overcomes theproblems mentioned above.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide anelectrical connector comprising contact elements firmly secured incontact receiving bores defined in an insulative body.

Another object of the present invention is to provide an electricalconnector comprising contact elements each having a resilientlydeformable section for accommodating strain caused by different thermalexpansions between the insulative body and a circuit board to which theconnector is soldered.

A further object of the present invention is to provide an electricalconnector comprising a number of contact elements each having aretention section offset from a main section thereof thereby allowing areduction of the thickness of the connector while maintaining the samemechanical strength to secure the contact element in the connector.

To achieve the above objects, an electrical connector in accordance withthe present invention comprises an insulative base defining a pluralityof contact receiving bores for each receiving a contact element therein.A cover plate is attached to the base to define a space therebetween formovably receiving a slide plate. The slide plate defines a plurality ofslots corresponding to the contact receiving bores of the base and eachslot retains a conductive member therein. The cover plate defines holestherein corresponding to the slots and adapted to guide pins of a chipmodule into the slots. The slide plate is movable between a releasedposition and an engaged position where the conductive member engageswith both the pin and the contact element to establish electricalconnection therebetween. Each contact element includes a solderingsection extending beyond the base and adapted to be soldered to acircuit board, and an engaging section extending into the correspondingslot for being engaged by the conductive member. A retention sectionfixed in the base is spaced from and connected to the soldering sectionby a connection section thereby allowing a reduction of thickness of theconnector without sacrificing the mechanical strength thereof. Theconnection section is resiliently deformable to accommodate a relativemovement between the retention section and the soldering section causedby a difference in thermal expansion between the connector and thecircuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent to those skilled in the art byreading the following description of a preferred embodiment thereof,with reference to the accompanying drawings, in which:

FIG. 1A is a plan view of a portion of a conventional connector when apin of a chip module does not contact a contact element of theconnector;

FIG. 1B is a cross-sectional view of FIG. 1A;

FIG. 1C is a plan view of a portion of the conventional connector whenthe pin is brought into contact with the contact element of theconnector;

FIG. 1D is a cross-sectional view of FIG. 1C;

FIG. 2 is an exploded view of an electrical connector constructed inaccordance with the present invention;

FIG. 3 is an assembled view of FIG. 2;

FIG. 4A is a plan view of a portion of the connector of the presentinvention with a cover plate removed when a conductive member retainedin a side plate does not engage with a pin of an external electronicdevice and a contact element retained in a base of the connector;

FIG. 4B is a cross-sectional view of FIG. 4A;

FIG. 5A is a plan view of a portion of the connector of the presentinvention with the cover plate removed when the conductive memberretained in the slide plate is brought into engagement with a pin of theexternal electronic device and the contact element retained in the baseof the connector;

FIG. 5B is a cross-sectional view of FIG. 5A;

FIG. 6A is a cross-sectional view of the base of the connector and acircuit board to which the contact element is to be soldered; and

FIG. 6B is a cross-sectional view similar to FIG. 6A but showing thecontact element soldered to the circuit board.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings and in particular to FIGS. 2 and 3, a zeroinsertion force (ZIF) ball grid array (BGA) connector in accordance withthe present invention comprises a base 8 having a bottom wall 89defining contact receiving bores 81 in a top face 86 thereof forreceiving contact elements 9, and two opposite side walls 80 extendingfrom the bottom wall 89 defining a space therebetween (not labeled) forslidably receiving a slide plate 7 therein. The slide plate 7 is guidedby the side walls 80 to move between a released position (FIGS. 4A and4B) and an engaged position (FIGS. 5A and 5B). A cover plate 5 isattached to the base 8 to enclose the slide plate 7. The base 8 formsthree barbs 82 on each of the side walls 80 thereof. The cover plate 5forms two elongate flaps 53 respectively extending downwardly from twolateral sides thereof. Each flap 53 extends the entire length of itsrespective lateral side of the cover plate 5. The cover plate 5 definesthree openings 52 in a top face (not labeled) along each lateral sidethereof and adjacent an inner surface (not labeled) of the respectiveflap 53. The cover plate 5 and the base 8 are assembled together byengaging the barbs 82 with the flaps 53 at a position just below theopenings 52.

The slide plate 7 defines a number of slots 72 corresponding to thecontact receiving bores 81 of the base 8 for partially receiving thecontact elements 9 therein. The slots 72 are dimensioned to notinterfere with the contact elements 9 during movement of the slide plate7 between the engaged position and the released position. The coverplate 5 defines a number of holes 51 therein corresponding to the slots72 of the slide plate 7 for entry of pins 4 (FIGS. 4A, 4B, 5A and SB) ofan external electronic device, such as a central processing unit chip(not shown), into the slots 72.

A driving plate 6 is pivotally attached to and interposed between thebottom wall 89 of the base 8 and the cover plate 5 with a manualoperating section 62 extending beyond an edge 87 of the base 8 forexhibiting manual access to rotate the driving plate 6 between a firstangular position and a second angular position. The driving plate 6 hasa cam portion 61 forming a camming contour engaged by a follower section73 formed on the slide plate 7 whereby rotating the driving plate 6between the first angular position and the second angular positioncauses the slide plate 7 to move between the engaged position and therelease position.

In the embodiment illustrated, the cam portion 61 is formed by a curvedrib which is movably received in an opening 71 defined in the slideplate 7. The opening 71 has an inward projection contacting the curvedrib of the cam portion 61 to serve as the follower section 73 of theslide plate 7.

Referring to FIGS. 4B and 5B, each contact element 9 comprises a main(not labeled) constituting a soldering section 92 extending beyond thebottom wall 89 of the base 8 to be connected to a circuit board 3 (FIGS.6A and 6B) and an engaging section 93 extending into the correspondingslot 72 of the slide plate 7. The contact element 9 further comprises anoffset retention section 91 spaced from and substantially parallel tothe soldering section 92 and connected thereto by a connection section910. The retention section 91 is received and retained in a cavity 84defined in the bottom wall 89 of the base 8 and in communication withthe contact receiving bore 81 thereby securing the contact element 9 inthe contact receiving bore 81. The retention section 91 has barbs 911engaging with inside surfaces (not labeled) of the cavity 84 forretaining the retention section 91 in the cavity 84. It should be notedthat contrary to the prior art, the soldering section 92 of the presentinvention is free to move with respect to the base 8.

A conductive member 70 is retained in each of the slots 72 of the slideplate 7. The conductive member 70 has a first resilient arm 701 and asecond resilient arm 702, preferably in the form of a “U”. The resilientarms 701, 702 are dimensioned to respectively contact the engagingsection 93 of the corresponding contact element 9 and the pin 4 of theexternal electronic device when the slide plate 7 is moved from thereleased position to the engaged position. Electrical connection is thusestablished between the pin 4 of the external electronic device and thecontact element 9 of the connector.

In the embodiment illustrated, the retention section 91 of the contactelement 9 is arranged at the side of the soldering section 92 that isopposite the second resilient arm 702 of the conductive member 7 therebyproviding a more sound support of the contact element 9 against theforce acting thereupon by the contact with the second resilient arm 702when the slide plate 7 is moved toward the engaged position.

As shown in FIG. 6A, the soldering section 92 of each contact element 9has a free end projecting beyond a bottom face 88 of the bottom wall 89of the base 8 to which a solder ball 31 is attached for connecting thecontact element 9 to the circuit board 3. The solder ball 31 is moltenand connects the contact element 9 to the circuit board 3 as shown inFIG. 6B. Due to the difference in thermal expansion coefficients betweenthe base 8 of the connector and the circuit board 3, a relative movementbetween the retention section 91 and the soldering section 92 caused bydifferent expansions occurs during the soldering process as indicated byphantom lines shown in FIG. 6B. The connection section 910 between theretention section 91 and the soldering section 92 is resilientlydeformable thereby accommodating the relative movement occurring betweenthe retention section 91 and the soldering section 92. Thus, the solderball 31 connection is protected from being acted upon by excessiveinternal stress and the corresponding strain. A stable solder ball 31connection is thus maintained.

Preferably, a recess 83 is defined in the bottom face 88 of the base 8surrounding the free end of the soldering section 92 of the contactelement 9 for accommodating molten soldering material from the solderball 31.

In addition to allowing the soldering section 92 to freely move withrespect to the base 8, arranging the retention section 91 parallel tothe soldering section 92 rather than vertically stacking provides anadditional advantage of reducing a thickness of the bottom wall 89 ofthe base 8 without sacrificing the mechanical strength thereof forsecuring the contact element 9 in the contact receiving bore 81 of thebase 8.

Although the present invention has been described with reference to thepreferred embodiment, it is apparent to those skilled in the art that avariety of modifications and changes may be made without departing fromthe scope of the present invention which is intended to be defined bythe appended claims.

What is claimed is:
 1. An electrical connector adapted to be mounted ona circuit board for electrically connecting an electronic device to thecircuit board, comprising: a plurality of contact elements; aninsulative base defining a plurality of contact receiving bores for eachreceiving a corresponding contact element therein; a slide plate movablysupported on the base, the slide plate defining a plurality of slotstherein corresponding to the contact receiving bores of the base, eachslot being adapted to receive a pin of the electronic device; drivingmeans coupled to the slide plate for moving the slide plate with respectto the base between a released position and an engaged position forestablishing electrical connection between the pin and the contactelement; each contact element comprising a soldering section extendingbeyond a bottom face of the base to be connected to the circuit board,an engaging section extending into the corresponding slot of the slideplate to be electrically engaged by the pin, and an offset retentionsection spaced from and connected to the soldering section by aconnection section; and the slide plate comprising a conductive memberretained in each of the slots thereof, the conductive member beingconfigured to contact both the pin of the electrical device and thecontact element of the base when the slide plate is at the engagedposition for establishing electrical connection between the pin and thecontact element.
 2. The electrical connector as claimed in claim 1,wherein the connection section of the contact element is resilientlydeformable for accommodating a relative movement between the solderingsection and the retention section.
 3. The electrical connector asclaimed in claim 1, wherein the retention section is received in acavity defined in the base, the retention section having barbs engagingwith an inside surface of the cavity for securing the retention sectionin the cavity thereby retaining the contact element in the contactreceiving bore.
 4. The electrical connector as claimed in claim 1,wherein the conductive member of the slide plate comprises two resilientarms respectively engaging with the pin and the contact element when theslide plate is at the engaged position.
 5. The electrical connector asclaimed in claim 1, wherein the driving means comprises a platepivotally attached to the base and rotatable between a first angularposition and a second angular position, the plate forming a cammingcontour engaged by a follower section formed on the slide plate wherebywhen the plate is rotated between the first and second angularpositions, the slide plate is moved between the engaged position and thereleased position.
 6. The electrical connector as claimed in claim 5,wherein the camming contour is defined by a curved rib formed on theplate of the driving means, and wherein the slide plate defines anopening for movably receiving the curved rib therein, an inwardprojection being formed in the opening for engaging with the curved ribto serve as the follower section.
 7. The electrical connector as claimedin claim 5, wherein the plate of the driving means comprises a manualoperating section extending beyond the base and adapted to be manuallyoperated to move the slide plate between the released position and theengaged position.
 8. The electrical connector as claimed in claim 1,wherein the base comprises two opposite side walls defining a spacetherebetween for accommodating the slide plate therein, a cover platebeing attached to the base plate by being supported on the side walls toenclose the slide plate, the cover plate defining a plurality of holescorresponding to the slots of the slide plate for entry of the pins ofthe electronic device into the slots.
 9. The electrical connector asclaimed in claim 8, wherein each side wall of the base comprises barbsand the cover plate forms two flaps respectively extending downwardlyfrom two sides thereof, and the cover plate defines three openings neareach of the flaps, the barbs of each side wall of the base engaging witha corresponding flap of the cover plate at a position just below theopenings for securing the cover plate to the base.
 10. The electricalconnector as claimed in claim 1, wherein the free end of the solderingsection of each contact element has a solder ball attached thereto. 11.The electrical connector as claimed in claim 1, wherein the base definesa recess in the bottom face thereof surrounding the free end of thesoldering section of each contact element.
 12. An electrical connectorcomprising an insulative body defining a plurality of contact receivingholes in a top face thereof for each receiving a contact element, eachcontact element comprising a main section and an offset section spacedfrom and connected to the main section by means of a connection section,the offset section being received and retained in a cavity defined inthe insulative body, the cavity being in communication with the contactreceiving hole, the main section extending in a vertical direction witha soldering section at a bottom thereof, and the connection sectionextending in a horizontal direction so as to isolate the offset sectionto the soldering section.
 13. The electrical connector as claimed inclaim 12, wherein the offset section comprises barbs engaging with aninside surface of the cavity for securing the contact element in thecontact receiving hole.
 14. An electrical connector adapted to bemounted to a circuit board having a first thermal expansion coefficient,the electrical connector comprising a housing made of an insulativematerial having a second thermal expansion coefficient, the housingdefining a plurality of holes receiving contact elements therein, eachcontact element having a main section received and free to move in thecorresponding hole and having a free end extending beyond the housingfor being soldered to the circuit board, an offset section spaced fromand connected to the main section by means of a connecting section, theoffset section being secured in a cavity defined in the housing forretaining the contact element in the hole, the connection section beingresiliently deformable for accommodating a relative movement between theoffset section and the main section caused by a difference between thefirst and second thermal expansion coefficients.
 15. An electricalconnector adapted to be mounted on a circuit board for electricallyconnecting an electronic device to the circuit board, comprising: aplurality of contact elements; an insulative base defining a pluralityof contact receiving bores for each receiving a corresponding contactelement therein; a slide plate movably supported on the base, the slideplate defining a plurality of slots therein corresponding to the contactreceiving bores of the base, each slot being adapted to receive a pin ofthe electronic device; driving means coupled to the slide plate formoving the slide plate with respect to the base between a releasedposition and an engaged position for establishing electrical connectionbetween the pin and the contact element; each contact element comprisinga soldering section extending beyond a bottom face of the base to beconnected to the circuit board, an engaging section extending into thecorresponding slot of the slide plate to be electrically engaged by thepin, and an offset retention section spaced from and connected to thesoldering section by a connection section for retaining the contactelement in the insulative base.